Blue Glacier on the north side of Mount Olympus is a large glacier in one of the wettest mountain environments in the contiguous United States. Beginning near the mountain’s summits, it descends through steep icefall, crevasses, and a valley before ending on a barren rocky slope after retreating above a former lower icefall. Heavy Pacific-driven precipitation gives it more annual snowfall and rainfall than any other glacier in the lower 48 states, and its meltwater feeds Glacier Creek and the Hoh River through Olympic National Park to the Pacific. Like many glaciers, it has steadily shrunk in length and thickness since 1800, with notable losses measured in recent decades.